In glass syringes and other pharmaceutical packages, silicone oil is typically used as a lubricant to allow the plunger tip to slide in the barrel, and/or to promote draining of the intended deliverable fluid from the syringe surfaces.
Glass pharmaceutical packages or other vessels are prone to breakage or degradation during manufacture, filling operations, shipping and use, which means that glass particulates may enter the drug. The presence of glass particles has led to many FDA Warning Letters and to product recalls.
Glass-forming processes do not yield the tight dimensional tolerances required for some of the newer auto-injectors and delivery systems. Glass is also more difficult and expensive to fabricate into syringes than injection molded plastics.
An important consideration regarding medical syringes is to ensure that the plunger can move at a constant speed and with a constant force when it is pressed into the barrel during use, with a low initiation or breakout force, Fi, and a low maintenance force, Fm. A similar consideration making lubrication desirable applies to vessels such as pharmaceutical vials which have to be closed by a closure, for example a plunger tip, septum or stopper, and to the septum or stopper itself, and more generally to any surface which desirably provides smooth operation of moving parts and/or is protectively coated.
One factor affecting the magnitude and aging of the breakout force is the surface composition and topology of the syringe. Specifically, the breakout force is lower for glass syringes than for plastic syringes due to the surface energy differences between glass and plastic (glass is a hydrophilic surface and plastic is a hydrophobic surface). PDMS is hydrophobic. It would be useful to provide a similar breakout force profile on plastic and glass syringes, and for the effect of aging on the breakout force to be minimal.